Refining of oil



Nov. 26,1940.

A. C. VOBACH REFINING 0F OIL Filed April l0, 1957 .l I l I l l I I l Il USNQ ATTORN EYS Patented Nev; 2e, l194ev I 2,223;`14j1ffff 'feminin .vebeehiwhitinegfina;insiemi te 1 e Q Appli'eatien prit-1o, 1937, serial Ne. `136,078 1 qs,

This invention lrelates lto' improvementsinfthe tions. Theidiluent vblendslofv this invention; due

VAdetvaxingof hydrocarbon-oils-and nioreparticue partly tojtheirhigh solvent capacity for oilatslow larly-tothe dwax'in'g of`pto1eumgstocks-in the temperatureselnake -impossible to directly precipimanufacture'o' lubricating foils. vThe invention tatefromthe',stoekdiluentfmixturera iwax :of

provides-inipiove'ddiluent-llolendstvhich result in markedgpurity'and high Vmelting point. i l v e 5" 'increased economyf'and efficiency. ofthe devvaxingv Y The maximumipr'oportion of diluent of this-inj `f opration. vention normally required to effect dewaxing is` ,4 f Stock:'to'betreatedby ydilutingfit Wthfa diluent Volume'iofi'stock to be dewaxed although greater flo? suchaspetroleum'napntnagfehilling this steek amountsimaybeused-withadvantaget *The-large m mixture' te precipitate thetwaxiand' Separating amount-Ofdilent'requiedsfmrethan .wmpe'n- Y the wax--f-rom tlflechilled 'stoclifatlow tempera: `sated for bythe many advantages Which nl enfb L ture."-'-More recermy it has been proposed to use obtainableby the vuse of diluents ordiluentblends vliquid `prc' pa .ne,4 methyleace'tate,and'*blends-o Y. heretofore knOWn-` 7 1 ll benzol and acetone, 'benz'o'l'; acetone vfand-toluoli The u'seof diluents of thisjinvention'idoes n`ot`1`5 y 'j andbenzolfand methylaceta-te 'fasldiluents inl such demand special fand expensive apparatus suchas g dlewaxingxoperations; l the high `pressureapparatusnecessari/3 for examfflheiimprove'd ydiluents `of-this invention eo'm- D16, fOi- 115e With liquid L'PI'ODane" Th-boiling .Y I fitpp'risez blends' pfnberizol, vbel-,3,.Agenti diehmrethyl range-of` the diluents .of this .invention-idonee. i "f 2|) ether;hereinaiterrvgenerally-referred1to=as-ether, SDOndfaDDIOXimaiely With'ihatfvf thevdilun's 2h and e, low freezing peint tnird-solventsuehfes in conventional use.v Accordingly, substantially l. toluene, ,lalmixture'pfitoluolriandxylol, vorit'he, like, standard'apparatus maybe-used t-oqjecov'erthe v,thean'muntof eachofthefso1vetie0fhe-blend diluents'of thisfinvention'fromthe products of j/ lying within definite limits hereinafter Inoreiully the vde'vvaxii'ig Opra/Giona' Y f F25 described. yThe improved diluents of this invenf: .The relativelvlwi'dei boilingrange ofthe dilueht'si. :25

tion have numerousadvantages, as will be appar- 0f this inventiona..176Ffiorbenz1e231'F-"for l' f l@neil1701711e'furthivClescripifnaj--, toluene'andzaltzgw.iF-lio?"beta'b'etafdchmr; t 'The dvil' ntsf LISI'jHVQHpiOn 11g@ nol demir ethyl etherassist materially iin'ininimizinglosses 1,- ,tal eietpn either oil orwax and havea liela-y 0f the diluenin These lO'SSeS'areinher'ehtlyhigh 'f y8i) 'v 4 p eiait'llresnv as-"vvell as at'- higher temperatures. tone or methyl acetateith'e boiling pointof. onli Theirlhigh k'soli/Vent oapacityfo' gilet 1ow,. 1;em merciala'cetone and methyl acetate being 132;- i ,e v pe'rat'uies minimizes-the retentionl oi oil in the Y 133F--2nd 135 F-flSpeCiiVely- L' f y s'p'jja-ted: arid thereby promotes a, Sharp sep.'` -Blends consistin'gisolelyof. benzol-fandftheeth'er '357'aatohfbetwee'oil and Wan'. have been `suggested as deminin'gldiluents,A 35

flhe'diluents of thisii'vention exhibit a ratio ofv use of such diluentfblends as previously-suggested i x1 solubility to oil 'solubility which-'diminishes is Open toy Yseveral serielleA objections."f'or'flin- "markedly u 1W temperatures; thesis, the dim.' stance, there is .a tendency? of the blends; to l'proj ents isliewa marked selectivity for eijlever weitet lduce an inferior lubricating -oi1V dficient inl bod'i'ry '40 Alow temperatures such as 20d-F., forexample'. and 9001 IWith respect il? I'its ViSGOSiY 4index: lo Cogent 'evidence of this advantage is observed in vlViOleQVel there iS 'ftendenyfbowa'd the 'frllna the raetthatit is not neeessaryto chill e. mixture tion Of an ether extrctphaseduring tnedeWaX- oithestockiand diluents-of this invention to'an n'g Operation thus `ini?lfflini A'Wiiihih`1C VY extremely lowtempereture to yieldaproduct havof the wax. I have. found, however, tiiatiwithin v 5, img aenoticeablylow pbur-'point`; Forexample, ii; certainv definite limitsfof'the proportions' ofthe 45 :isnpossible'itoobtaijprdugts of 10 p rpour test constituents of the? blend, these difficulties;l are i `v from1vvax-bearingi'stocks havngv'axviscosity oi. eliminated ihusnbtafininga'f Sl'lpei'iflkv iiWXin f about '53 seconds ati210=F. by chilling agnlixture DIOCE'SS- Y t t ofthe stock'and diluentstoaloolltI-ZOFKy l 5 MYinVeniiOn CDIPSSS; l2i0G01"'dini-Ehh,SU-.iJ'eif-Y e i -50 '-.'Il'1e'waxfprcipitated from a -n'i'iiitur'e of stock ing a Waxlbearing Pti'leum SOCkiOfthe rvi'fin" 50 o Vmd fdilu'ent'blends of this'invention vis in condi l -of a' diluent blend containing benzol'and beta'beta tion to vbe readilyrseparated'ffroml the mixture `by dichlorethyl ether, theproportionof the vetherin i .ltration.., The waxlisprecpitated'in a crystal-x the blendv lying betweenapproximately 20andf4()v 1 'l lized form andis Well-'adapted tosuloseql'ientpllripercenttof the"-total`voluni`e of the blend the exact Vj 55 `ication by Washing v:and: recr'ystalllzation opera;- `amount o'fetherldepending'upon the typeof stock 5,5

I erHere'tf'ore, itha'sbeeneustonlary'to deWa-Xthe about'i400 percent 'byvvoluine calculated upon thet ely high olventcapacitvfort lat'lQvvk/tem` for diluentsfcontainil'lgloenzol together ,Withace- 30 I i being treated. For example, the ether percentage limitations have been found to be about 25 to 40 percent, based upon the total volume of diluent blend, for treatment of a wax slop comprising an overhead wax distillate stock and about 20 to 30 percent for a heavy bottoms raffinate which has previously been subjected to a nitrobenzene-acid treatment.

I have discovered, furthermore, that when a blend of benzol and the ether-is subjected to the low temperatures of the dewaxing operation, say 20 F., the benzol, because of its relatively high freezing point, separates out, and that such phase separation is prevented Without detriment to the, operation or the products thereof by 'adding to the blend definite quantities of' a lower freezing, oil-miscible solvent such as toluene, xylol, or the like. A smaller amount of this lower freezing,

oil-miscible solvent than the definite quantitiesV hereinafter more fully described does not prevent the separation of benzol. The upper limits of the amount of this lower freezing solvent which may be fused are governed by the fact that the Waxyield and pour point of the resulting products are comparatively poorer as the amount of this solvent added tends .to displace Vthe benzol in the diluent blend.

VMy invention further comprises, therefore, subjecting a Wax-bearing petroleulnstock to the action of the above-described diluent blend which further contains definite quantities of a low freezing, oil-miscible solvent such as toluene, xylol, or the like. The optimum proportion of the lower freezing solvent varies somewhat with the stock vbeing treated. For instance, in deWaX- ing an overhead Wax distillate stock, I have found that the proportion of toluene should not be substantially lower than approximatelyA 10 percent based on the benzol-toluene content of the blend and not substantially lower than approximately 25 percent in dewaxing a heavy bottoms raffinate which has previously been subjected to a nitrobenzeneacidtreatment. I-Iowever, where the benzol used' in the blend is of a commercial type containing toluene or similar low freezing constituent as impurities, it will be necessary to add to the blend only suiiicient low freezing solvent to bring Vits total. content to the above stated proportions;

The process of my invention mayr be more clearly understood by a consideration of the accompanying flow diagram. As indicated by the solid lines in the diagram, the charging stock to be dewaxed and the three solvents (beta beta dichlorethyl ether, Abenzol and toluene) are'taken from their respective storage tanks incorrect volumetric proportions and pumped into a blending tank which is equipped with means such as a heating coil for raising the temperature of the mixture and means for agitating `the mixture. The mixture is therein thoroughly agitated and heated to about 100 to 120 F. after which the warm` mixture is pumped through suitable chillin g lequipment to reduce its temperature t about 10 to 20 F. The chilled mixture is thenypassed to a, suitable lter, and the dewaxed oil-solvent mixture and wax-solvent slurry pass from the iilter into their respective run tanks. The dewaxed oil-solvent mixture and wax-solventl slurry are pumped from :their respective run tanks to separate solvent recovery distillation units from which the three solvents, stripped from the Wax and dewaxed oil, are returned to their respective storage tanks for refuse, thus completing the solvent cycle. 'Ihe solvent-free Wax and dewaxed oil from the solvent stripping units are finally pumped to their respective run tanks and are then ready for any further treating or finishing operations which may be contemplated.

An additional step may be incorporated in the process for the purpose of more completely Washing the `oil from the wax cake. When used, the solvent washing step as indicated by the dotted lines on the fiow diagram is accomplished by mixing the three solvents (the ether, benzol and toluene) together in a suitable tank in substantially the same proportion in which the solvents weren mixed in the primary waxy-oil treatment. The wash solvent mixture is then chilled to substantially the dewaxing temperature usednin the primary treatment and forced through the wax p cake Adisplacing the oil therefrom. For example,

Where drum type continuous filters are used the wash solvent mixture may be forced through a perforated spray pipeor series `of spray nozzles onto the ,surface of the Wax cake. The mixture of oil and solvent is removed from the filter to-` gether4 with then dewaxed oil-solvent mixture of the primary treatment and pumped into the dewaxed oil run tank for subsequent separation,

It should be understood, however, that the washing of the Wax cake on the filter with a cold solvent mixture is not an essential step in the dewaxing process in all cases. For example, Where light distillate stocks, which are characterized by large free-filtering wax crystals, are being deWaXed or When large amounts ofthe solvent mixture are used in the primary dewaxing treatment, that is when 500 to 600% of the solvent mixturev is used, the washing step may not be necessary. It is usually desirable, however, to use the solvent washing operation-When a wax isbeing separated froma heavy stock such as heavyv Wax slops or heavy bottoms rafnates.

The Ifollowing examples of operation'embodying the use of the Vnovel diluents will further'illustrate the invention:

Example I An undewaxe'd Wax slop comprising overhead wax distillate stock having a gravity of 29.2, a viscosity of 53.1 seconds at 210 F., and a pour test of 100 F. was diluted with 400% of its own volume of a blend of 67.5% benzol, 7.5% toluene, and2,5% ether. `After chilling to 20 F. and retreatment with 400% of the same diluent blend, a wax yield of 24.3% (based on the stock) was separated from the. mixture `by filtration. The Wax had a gravity of 33.4 and a' melting point Vof 1'10.7 F.; the stripped raffinate had a gravity `of 27.5, a viscosity index of 92.5, and a pour test of F. f

Example II An undeWa-xed Wax slop comprising-overhead wax distillate stock having a gravity of 29.2, a viscosity of 53.1 seconds at 210 F., and a pour test of 100 F. was diluted with 400% of its own volume of a blend of 54% benzol, 6% toluene, and 40% ether. After chilling to 20 F. and retreatment with 200% of its own volume of the same diluent blend, a ,Wax yield of 26.8% (based on the stock) was separated from the mixture by filtration. The Wax had a gravity of 35.0 and a melting point of 109.3 F.; the stripped raffinate had a gravity of 27.1, aviscosity index of 88.4, and a pour test of F.

y l Example III'w i'. An/undewaxed waxY slop comprising `-overlfread l flirter'distillate;stockl having a gravity off29ff2. a

.viscosityvof 53.1;seconds at 210 rF., a nd 'amour t ltreatment with 200% of the samediluent blend,-

'vermeld of l17.5% (paseaba the am?) 'separated from the mixture by-iiltration. .The-

, -,wax fhad afI gravity' of 35.3 and a 'melting point of 1 17.4-F.; the stripped raffinate had; a gravity of 27.8, a viscosity index of 88.9, anda pour test of" F.. g w v f f Example IV A Anitrobenzene-acid raffinate comprising a heavy bottoms raffinate having a'gravity ofr26.4, a viscosity of 171.5 at 210 F., and a pourtest of 60 F.'was diluted with 400% of its own'volume of a blend of 60% benzol, 20%y toluene, and 20% ether'. After chilling to -20"v F. and uponrertreatment with 200% of the'same diluent blend,

a wax yyield of 17.9% (based on the stock) was separated from the mixture'by filtration. The

f. wax had a gravity of 28.9 and aj melting point of fao 120.8"F.;the stripped raffinate had a gravity of 26.1, va viscosity index of. 103.8, and a pour test of F.

Example VV A nitrobenzene-acid raffinate comprising a y -heavy bottoms raffinate having a gravity of 26.4, a. viscosity of 171.5 at 210 F., and a pour test'of 60 F. was diluted'with 400% of its'own volume of la blend of 52.5% benzol, 17.5% toluene, and 30% ether. treatment with 200% of the same diluent blend,

f a wax yield of 20.5% was separatedfrom the mix` ture by ltration; the wax had a gravityvrv of 27.5 and a melting point of 119.8 F. The vstripped r'afnate had a gravity of 26.4, a viscosity index f of 103.8,and a pour test of 20F.

Example VI of 35.6 .and la'melting point of 123.6 F. The

stripped rafnate had a gravity of 27.3', a viscosity index of 88.1, and .a pour test of -'5 F.

' 'f In general, the ether-benzol-toluene dewaxin process is independent of other refining operations to which the oil may be subjected. However, theV dewaxing process of my invention may beused` in conjunctionwith a rening operation in which beta beta dichlorethyl ether is the refining solvent.

In such a casethe raffinate containing a considerale-le amount of the ether may'b'e subjected directly .to the dewaxing yprocess of my invention. without intermediate stripping of the refining solvent from the raffinate. The ether content of the ranate-ether mixturemay -be readily deytermined and benzol and toluene may then be added to the rainate-ether mixture in the blend` ing tank of my process together with any addi-A tional amount of v the ether which maybe necessary to make up the desired ratioof ether-benzol- After chilling to -20 F. and re-v tolu'eneiin therdewaxing'zoperation. "a:cdm-iy :'ibin'eclf solventIk extraction' and :solvent idewaxing :operationmayfbezc'arriedfoutwhennsingthe improved dewaxing solvent. blend of im'yinvention t Asusedherein; the termf'fpour test is the 'low-y f festtemperature @at vvllicliv :th'ezoil .ow fwhen i chilled Lwithoutfdisturbance, determined, for fexammeinaccerdance WithfmethOamT-So.ofthe American? society'- -for v III-fistingl* Material.- 1Vis' s cositi'esementioned*herein lare visclosities 'inisec- 'onds'Sayblt Universal.' "Theperce'ntag'eslofthe constituentsl of the'diluent blends set forth in the K preceding examples and f in'fthe claims lareffthe percent' es offfthe respective constituents fwith rvresp'eet-1nithe-tfstn lvenian or duuentbled. f

Ity will be seen, therefore, that my invention comprises an efcient and inexpensive methodgof dewaxing wax-'bearing petroleum lattacks by the yusev of an improved ldi-luent blend whereby a wax of high degree of purityis obtained-and an lin--v proved petroleumproduct is obtained which hasA an advantageous low pour point.

In the specific examples appearing herein I1 n' have Villustratedmy invention as applied toun-l dewaxed wax slop and to a heavy ramnate. It is to bev understood, however, that the invention is Y not limited to the treatment of such stock but contemplates the treatment of any wax-bearing petroleum stock. The speciiic proportionsof the constituents of thevblend given in the foregoing examplesare those which I have found most suit- I able to the treatment of the specific stocks selected for the purposeof illustrating my invention and will vary within the specified ranges with the characteristics of the particular wax-bearing` stock to be treated, as will be readily understood by one skilledin the art in view of the foregoing examples. Similarly the optimumv proportion of the low freezing constituentof the blend for a .particular stock will vary somewhat with the temperature to which the mixture is chilled.

1. In the solvent .dewaxingof a wax-bearing which comprises separating wax from the stock in the presence of a diluent blend comprising be# petroleum stock in which the stock kanda diluent i are chilled to about F., the improvementy tween and 40 percent beta beta dichlorethyl l ether rand the remainder comprising a mixture of benzol and toluene in which the toluene content/'of said mixture isnot substantially less than labout 10 percent.

2. In the 'solvent dewaxing of a wax-'bearing petroleum stock in which the stock and a diluent are chilled to about -20' F., the improvement which comprises separating rwaxfrom the stock, in the presence of a diluent blend comprising between 20 yand 30 percent beta beta dichlorethyl ether and the remainder comprising a mixture of benzol andtoluene in which thev toluene content of said mixture is not substantially less than about 25 percent.

43. A dewaxing diluent blend for dewaxing a wax-bearing petroleum stock at a chilling' temperature of about 20 F. which `comprises be tween 25 and 40 percent `beta beta dichlorethyl ether and the remaindercomprising a mixture of benzol land toluene in whichthe toluenev cnn-1` substantially less'thanV tent of said mixture is not about 10 per cent. a

4. A dewaxing diluent-blend .for dewaxing a. wax-bearing petroleum stock at a chilling ternperature of about 20v F. which comprises between 20 and 30 percent beta beta dichlorethyl ether Vand theremander comprisingV a mixture of benzol and toluene in Whichthe toluene content ofsaid mixture is not substantially less than about 25 percent.v t v I n 5. In. the solvent dewaxing, of va Wax-bearing petroleum stock in which the stockf and a diluent are chilled` to about -20 F. with a diluent blend comprising beta beta dichlorethyl ether and -benzol 'wherein the diluent blend has a tendency 10 to separate out into several phases during the de- .Waxing operation and the stock v and diluent 15 such anV amount-as to substantially eliminate the separation of phases during the dewaxing' ope@- tion.

6. In the solvent dewaxing of a Wax-bearing petroleum stock in which the stock and a. diluent areclfiilled to about 20 F. with a. diluent blend comprising beta beta dichlorethyl ether and benzol wherein the diluent blend has a tendency to separate out into several phases during the dewaxing operation and. the stock and diluent blend is chilled to about 20 F., the improvement which Vcomprises preventing the separation of phases by adding to the diluent blend an amount of toluene not substantially less than about 10%.

ARNOLD C. VOBACH. 

